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Substructure Model is Getting Diverged
Hello Mr. David,
Hope you are well. I am facing a serious problem analyzing a very simple floater/stabilizer system connected with a rigid riser. During the simulation, the model is getting diverged after 400 seconds. The graph shows peculiar values though the 3D view seems to be working absolutely fine. I have got absolutely no idea about what is happening. Can’t find a problem in the substructure definition file. Can you please look at the problem?
Best regards
S.H.M. Labib Mahmud
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Hello Labib Mahmud,
the issue is that you have not constrained the Transition Piece (TP).
Even if you are not using a turbine, the TP is a part of the simulation. If the TP is not constrained it is “free falling” as you can see in your plots. At some point the velocity of the TP has grown so large that the structural model diverges.
To fix this just connect the TP with some part of your structure, or fix it to the ground. To connect it to JNT_1, simply paste this line into your SUBCONSTRAINTS table:
4 1 0 1 0 0 1 1 1 1 1 1
That line constraints your TP to JNT_1, which will resolve the issue. The TP itself has near zero mass associated with it, so it wont affect the dynamic results of your simulation – but even its near zero mass is enough to accelerate the TP to the point of divergence if its not fixed via a constraint!
BR,
David
